1. Field of the Invention
The present invention relates to a solar battery which utilizes an oxide semiconductor. More specifically, the present invention relates to a solar battery in which at least an electrolyte and a porous member of an oxide semiconductor retaining a pigment material are provided between a transparent electrode and a counter electrode, and whose conversion efficiency has been increased by improving the contact between the transparent electrode and the porous member of the oxide semiconductor.
2. Description of the Related Art
As solar batteries, silicon of single crystal, polycrystal, or amorphous type have been so far used for their semiconductor materials; however, solar batteries with such silicon have a disadvantage of high production cost.
For this reason, in recent years, development of solar batteries utilizing inexpensive oxide semiconductors such as a titanium oxide has been considered.
However, since an oxide semiconductor made of a titanium oxide or another oxide mainly absorbs light from outside the ultraviolet range, solar batteries utilizing an oxide semiconductor have an extremely poor utilization efficiency of sunlight, resulting in a low conversion efficiency.
In order to solve this problem, it has been tried to improve the utilization efficiency of sunlight by adding a pigment to such an oxide semiconductor. In particular, it has been suggested, in recent years, to improve a conversion efficiency in a solar battery with an oxide semiconductor by using a porous member as an oxide retaining member so as to increase the surface area and make the porous member retain the pigment.
One such solar battery comprising a porous member of an oxide semiconductor retaining a pigment is shown in FIG. 1, in which a transparent electrode 2 made of a tin oxide or the like is provided on the surface of the transparent substrate 1 made of a glass substrate or the like, a porous member 3 of an oxide semiconductor made of a titanium oxide or the like is further provided on the transparent electrode 2, and a pigment material is retained by the porous member 3 of the oxide semiconductor. Furthermore, an electrolyte 6 is provided between the porous member 3 and the counter electrode 5 disposed on the substrate 4, and a sealing member 7 is provided so as to seal their circumference.
In forming the porous member 3 of an oxide semiconductor onto the transparent electrode 2, according to a conventional method, a disperse solution of the oxide semiconductor is applied onto the transparent electrode 2 and then the electrode 2 is sintered so as to form the porous member 3 of the oxide semiconductor.